1. Field of the Invention
The present invention relates to unmanned helicopters, and more specifically to an unmanned helicopter including a body cover including a plurality of air vent portions.
2. Description of the Related Art
There is a conventional unmanned helicopter which includes a body cover having a plurality of air vent portions (e.g., holes for air to pass through). For example, JP-B No. 4574841 discloses an unmanned helicopter which includes a main rotor, an engine for driving the main rotor, a body cover covering the engine, and a radiator through which an engine cooling water circulates. The radiator is located at an opening of the body cover. The body cover includes a first vent hole provided below the radiator, a second vent hole provided behind the engine and on an upper surface side of the body cover below the main rotor, and a third vent hole provided behind the engine and on a lower surface side of the body cover. Accordingly, in the unmanned helicopter it is possible to allow outside air to flow into the body cover, and allow air inside the body cover to flow out via the opening, the first vent hole, the second vent hole, and the third vent hole. This arrangement makes it possible to reduce a temperature increase of the air inside the body cover, thus reducing a temperature increase of various components of the unmanned helicopter (such as the engine, control devices, etc.)
In the field of the unmanned helicopters as described above, there is a demand in recent years for the use of high-performance engines. However, if a high performance engine is used, the amount of heat generated by the engine increases, and the engine temperature tends to increase. This tends to increase the temperature inside the body cover. In particular, when the unmanned helicopter is flying forward at a high speed, the engine has a high output and therefore the engine generates a large amount of heat. As a solution for this problem, the unmanned helicopter according to JP-B No. 4574841 includes a plurality of radiators in order to reduce the increase in the engine temperature. However, in this case, the unmanned helicopter has an increased weight.